1. Technical Field
This invention relates generally to the field of data networks. In particular, it relates to a method and apparatus for segmenting concatenated variable-size packets of a data stream in order to simplify network design and increase transport efficiency while observing delay constraints to ensure high-performance.
2. Description of the Related Prior Art
A data network comprises a number of source nodes, each source node receiving traffic from numerous traffic sources, and a number of sink nodes, each sink node delivering data to numerous traffic sinks. The source nodes can be connected to the sink nodes directly or through core nodes.
The design of a data network is significantly simplified if data is transferred in fixed-size packets. However, typical data sources generate packets of variable sizes. A common approach, used in ATM for example, is to segment each packet individually into ‘cells’ of a predetermined size. A last cell of each packet would then be filled with null data. It is possible then that a large proportion of the cells become poorly utilized, depending on the packet-size distribution and the selected cell size. This can lead to relatively high capacity waste. For example, if the cell size is 1000 bits and the packet size for a high proportion of packets is within the range 1000 to 1200 bits, the relative capacity waste can be of the order of 40%. With the varying nature of data composition, it is difficult to characterize the data and to standardize a cell size that optimizes capacity utilization. Capacity waste is not only costly, but it also limits network scalability.
U.S. Pat. No. 5,930,265, issued to Duault et al on Jul. 27, 1999, describes a data processing method for efficiently transporting multimedia packets over a network that serves packets of fixed length. The method includes a step of concatenating the multimedia packets, generated by a number of users, and appending the concatenated data packets with a sub-header that identifies the individual packets. The method is primarily concerned with low-speed data and the aggregation delay is not taken into consideration.
Methods of packet concatenation that aim at minimizing capacity waste under delay constraints are required in order to realize efficient high-performance networks.